Fix homserver configuration url

roles/matrix-bot-maubot/templates/config/config.yaml.j2

@@ -57,7 +57,7 @@ server:
 homeservers:
   {{  matrix_domain }}:
     # Client-server API URL
-        url: {{ matrix_server_fqn_matrix }}
+        url: "https://{{ matrix_server_fqn_matrix }}"
     # registration_shared_secret from synapse config
     # You can leave this empty if you don't have access to the homeserver.
     # When this is empty, `mbc auth --register` won't work, but `mbc auth` (login) will.